Prurigo Nodularis (PN) is an intensely pruritic dermatologic condition with the presence of papules as well as nodules with excoriations and ulcerations. The basis of PN is a pre-existing severe and chronic pruritus of various etiologies. The pruritus leads to scratching. However, the etiology or predisposing factors which lead to the development of the papules and nodules of PN are largely unknown (Eigelshoven et al 2009; Valdya and Schwartz 2008; Lee and Shumack 2005). Iking et al (2012) reports that in the past few years the hypothesis for the etiology of PN as being a reaction pattern due to a “vicious cycle of repeated itching and scratching” is gaining wider acceptance in the medical community.

In October 2016, Trevi announced positive study results from a Phase 2 trial conducted in 62 patients with moderate to severe prurigo nodularis. The proportion of patients in the Nalbuphine® ER 180 mg BID arm meeting 50% responder criteria at week 10 or last observed visit (MITT population with n=18) approached statistical significance (p=0.083), and this arm met statistical significance for patients (n=12) completing treatment (p=0.028). Change from baseline in the ItchyQoL™ total score (22 questions that measure how pruritus affects a patient’s quality of life), was significantly more favorable for the Nalbuphine® ER 180 mg BID dose compared to placebo (p=0.022). The multi-center, randomized, double-blind, placebo-controlled, parallel, three-arm study evaluated the safety and anti-pruritic efficacy of Nalbuphine® ER tablets dosed twice-daily at 90mg and 180mg in 62 patients in the United States and Europe. Patients with moderate-to-severe itch intensity, defined as ≥ 5 on the 0-10 Numerical Rating Score (NRS) scale, were enrolled to evaluate drug efficacy across a representative patient population for treatment of this chronic indication. The actual average baseline worst itch for enrolled patients was ≥ 8, indicating the severe nature of the disease. The study consisted of a titration period of two weeks, followed by an eight-week blinded period on a fixed dose of drug or placebo, and a two-week wash-out period. Trevi is also conducting a one-year open label extension study to determine the long-term safety in this population, as well the potential long-term impact on the healing of nodules and papules.